In the prior art, a switching node has peripheral devices (connection devices for subscribers or lines), a central computer platform, a message distribution device, and other central units (coupling field, protocol termination devices (e.g., #7), background memory, operating devices). The relationships in this regard are shown in FIG. 1.
The peripheral devices fulfill essential switching technology tasks tied in with the voice channels of the peripheral device. They therefore contain switching technology programs, operating technology programs, and administrative programs, as well as data related to the device, such as connection locations, signaling, authorizations, telephone numbers, individual characteristics of connection lines and subscriber connections, as well as the extension state and configuration of the peripheral device.
The central computer platform coordinates control when establishing and ending a connection, as well as for reactions to administrative and error-related configuration changes.
The peripheral devices are connected with one another and with a common computer platform by a message distribution system. The other central system components make special functions available for the switching system, e.g., for switching voice channels through, for processing signaling protocols, for implementing the operator interface, or for memory for mass data.
For reasons of fail-safe reliability, the central components of a switching system are designed to be redundant (e.g., doubled). The peripheral devices are generally not structured to be redundant. In the case of stricter failure requirements (e.g., rescuing stable connections beyond the failure of a peripheral device), however, peripheral devices can also be redundant.
Remote switching devices of a switching center (Remote Switching Unit, RSU), which include peripheral devices, just like the related switching center (parent switching center), have a local coupling field, and support local switching traffic, can be set up remotely from the parent switching center. In this connection, the transmission segment between the remote switching center RSU and the parent switching center V generally has a smaller bandwidth than the connection bandwidth of the total of the peripheral devices contained in the remote unit, because of the internal traffic in the remote unit. Therefore, for reasons of simplicity, the full bandwidth corresponding to the number of peripheral devices of the remote unit RSU is made available again at the coupling network of the parent switching center. The relationships in this regard are shown in FIG. 3.
If signaling and voice are carried in a disassociated manner, by separate paths, and if the peripheral devices only have the task of protocol processing and/or conversion, without physical termination of the voice channels, the restrictions of the peripheral devices with regard to resource pool and number of voice channels that can be terminated are eliminated. In this case of use, the peripheral device is determined, with regard to its capacity, by the performance capacity of the processors, as well as by the size of the memory and the capacity of the message interface.
Since more than one direction has to be made available for switching voice through between the A subscriber and any B subscriber, two different peripheral devices PE are generally involved in establishing and ending the connection (FIG. 2).
In this case, the restriction concerning the physically determined maximum number of connection lines that can be terminated is eliminated. This makes it possible for a peripheral device to process more than 120 connections at the same time, for example. The relationships in this regard are described in European patent application EP 99123208.3. According to this application, such a peripheral device can be capable of running multiple times on a real peripheral device, resulting in functionality of the connection control of n times 120 (n×120) connections on a real peripheral device, for example.
Without further optimizing measures, however, it is necessary to fully extend the related main coupling network of the switching center. This is also particularly true for all of the virtual peripheral devices that can run on a real peripheral device, although these do not require any voice switch-through capacity in the case of use described above.
If peripheral devices of remote units RSU are used for connection control of connections carried from outside the switching center, and if virtual peripheral devices of the remote units RSU are included for this, the coupling interfaces provided for these virtual peripheral devices on the coupling network also remain unused. This results in a greater space requirement of the switching center (footprint) as well as increased hardware costs and operating costs of the switching center.